It is known that a wall surface suction-type travel device as is described in US 2007/0235238 is, for example, capable of traveling between wall surfaces that intersect each other at right angles. The wall surface suction-type travel device includes two suction modules having respective wheels and being designed to be suctioned onto a wall surface. The two suction modules are coupled to each other via a hinge in a direction along which the suction-type travel device travels. This configuration allows one of the suction modules to pivot relative to the other suction module on a pivot axis extending in a direction perpendicular both to a direction in which the suction-type travel device faces the wall surface and the travel direction. An angle at which the modules pivot relative to each other is controlled by a hinge motor.
Unfortunately, the wall surface suction-type travel device described in US 2007/0235238 requires using the hinge motor and a controller to control the hinge motor. A transfer of the suction-type travel device from a wall surface to an overhung surface such as a ceiling surface, for example, necessitates controlling the hinge motor with high accuracy such that the proceeding suction module comes into contact with the overhang surface while maintaining a proper posture. Consequently, the suction-type travel device needs to have a complex configuration in order to reliably transfer from a wall surface to an overhung surface such as a ceiling surface.